Regulation of starch contents in potato (Solanum tuberosum L.) by manipulation of sucrose synthase gene

Transgenic potato microtubers were created in which the expression of sucro se synthase (Susy) was altered by introducing a chimeric gene containing th e coding region of Susy that is linked to the patatin promoter in sense (S) or antisense (AS) orientation. The analysis of transgenic microtubers show ed that Susy activity and starch content increased in S plants 8, 22, and 3 0 transformed with the chimeric sense gene; they decreased in AS plants 3 a nd 10 transformed with the antisense gene. RT-PCR analysis revealed that th e level of mRNA for Susy increased in S plants, and decreased in AS plants. There was a little change in the expression of genes for ADP-glucose pyrop hosphorylase (AGPase), one of key enzymes in starch biosynthesis. The level of mRNA for AGPase and the activity of the enzyme increased in S 8 plant, but decreased in AS 3 plant.